听力原文： Today I'd like to continue to talk about the reason why the United States developed at such a high speed in the past 400 years. There are many factors. America has an abundance of natural resources including some of the best farm lands in the world. People from many countries settled them, bringing with them a wealth of knowledge and skills. But in the last 100 years it has been the workingman that was the backbone of the nation. What is the American workingman? He's a worker in a shoe factory or a meat packing-house or a coal mine. But more than that, he is a husband and a father. He raised his children to value the importance of cooperation. And he raised his children to help them better themselves. Seldom do their children forget the value they have learnt at home. The workingman fought hard to achieve what he has for almost all his life, but today the workingman is faced with a new kind of struggle. Ever advancing technology is taking his job. It's very probable that the workingman will be replaced by a machine. (23)